The present invention relates to an apparatus for preheating a fuel-air mixture between a carburetor and the intake manifold of a combustion engine, and more particularly, to adding a redirection means to such apparatus to guide the distribution of such mixture into the manifold.
In carburetion systems for automotive combustion engines, fuel and air are mixed in suitable porportions for delivery to the intake manifold of an engine for combustion. In such an arrangement, it is important that the fuel, e.g., gasoline, be vaporized as much as possible and mixed with the air to obtain maximum fuel efficiency and to minimize release of unburned hydrocarbon polutants to the atmosphere in the engine exhaust. However, particularly where the engine, at start-up, is cold and the fuel temperature is low, a significant portion of the fuel may not be vaporized and the air-fuel mixture delivered to the engine manifold can include droplets of liquid fuel with the resultant partial combustion of such fuel mixture and the increased polutants in the exhaust emissions referred to above.
Attempts have been made to improve the vaporization of the above fuel-air mixture by preheating the mixture before it enters the manifold. Accordingly, preheaters, including heaters formed of conductive material of positive temperature coefficient (PTC) of electrical resistivity, herein PTC resistors or heaters, have been employed. Typically, the heaters are multi-passaged PTC resistors having at least a pair of spaced electric contacts connected to e.g. a DC power source and current is directed through such PTC resistor to heat it and its passages and the fuel-air mixture passing therethrough, to provide a more complete evaporation of the liquid fuel in such mixture. See for example, U.S. Pat. No. 4,141,327 Marcoux et al (1979) and related U.S. Pat. No. 4,108,125 Marcoux et al (1978). For related and earlier prior art in which resistance heaters in the form of metal wires or grids are mounted in the flow of the fuel-pair mixture between a carbuetor and an engine manifold to preheat such mixture for fuel evaporation purposes, see U.S. Pat. No. 3,934,569 Bobene (1976) and U.S. Pat. No. 3,952,716 McCauley (1976).
For a baffled preheater chamber having a heat-exchange jacket mounted between a carburetor and an engine manifold, see U.S. Pat. No. 3,645,243 Ohlsson (1972). The baffle plates in the above chamber serve to create turbulance in the fuel-air mixture to assist the mixing thereof. The baffles provide no direction control for such mixture.
Accordingly, the fuel-air heaters of the prior art are concerned with immproved fuel evaporation of the mixture before it enters the engine manifold and make no suggestion of controlling the direction of such mixture as it enters the manifold. Accordingly such preheated mixture is often not accurately directed into the engine manifold so as to obtain uniform distribution of such mixture in the respective combustion chambers of the engine so that some chambers burn relatively lean (less fuel, more air) than other chambers of such engine, which can result in engine roughness and inefficiency of combustion. The adverse effects of misdirection of the fuel-air mixture into the engine manifold are exacerbated the more the carburetor discharge passage is mounted off-center relative to such intake manifold. Accordingly there is a need and market for a fuel-air mixture redirection apparatus which provides improved fuel-air distribution to the manifold and the respective combustion chambers thereof, and that substantially overcomes the prior art shortcomings.
In considering the above prior art fuel distribution problem, we considered constructing a baffle plate to be installed in the engine manifold to redirect the above fuel-air mixture. However, it was determined that such baffle plate would require installing an extra part in said manifold, and further, due to tooling requirements in mass production would be very expensive. Also considered was mounting a baffle to the underside of the fuel preheater which is mounted between the carburetor and the engine manifold. Again, this would require manufacturing an extra part and the additional step of mounting such baffle to project from the preheater in such a way as to redirect the fuel-air mixture, but not to block the flow thereof, an unsatisfactory and expensive alternative.
After review of such alternatives, the inventors discovered a low cost and effective apparatus to accurately redirect the fuel-air mixture, which apparatus can be readily manufactured in mass production.
There has now been discovered a structural member which can be added to a fuel preheater at low cost and ease of manufacture to provide a "baffle effect" to control fuel-air mixture direction and distribution and at the same time avoid problems inherent with construction and installation of baffle plates, as discussed above.